/**
*      author: Y_Yao
*      created: 2025-03-12 21:25:43
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 9e18;
const int INF = 0x3f3f3f3f;
const int N = 2e5 + 7;
int n,m;
int fa[N],sz[N],sz2[N];

int find(int x)
{
    return fa[x] == x ? x : fa[x] = find(fa[x]);
}

void Union(int u,int v)
{
    u = find(u);
    v = find(v);
    if(u == v)
    {
        sz2[u]++;
        return;
    }
    if(sz[u] > sz[v]) swap(u,v);
    fa[u] = v;
    sz[v] += sz[u];
    sz2[v] += sz2[u];
    sz2[v]++; 
}

void solve()
{
    cin >> n >> m;
    for(int i = 1;i <= n;i++)
    {
        fa[i] = i;
        sz[i] = 1;
    }
    for(int i = 1;i <= m;i++)
    {
        int u,v;
        cin >> u >> v;
        if(u == v) sz2[u]++;
        else
        {
            Union(u,v);
        }
    }
    for(int i = 1;i <= n;i++)
    {
        if(fa[i] == i)
        {
            if(sz[i] != sz2[i])
            {
                cout << "No" << endl;
                return;
            }
        }
    }
    cout << "Yes" << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}